1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method for forming a film of a coating liquid on a substrate.
2. Description of the Background Art
A rotary substrate processing apparatus is used for forming a film of a coating liquid such as a photoresist liquid (hereinafter abbreviated as a resist liquid) on substrates such as semiconductor wafers, glass substrates for liquid crystal displays, photomasks, and optical disks.
In a resist coating method and a resist coating apparatus described in JP 11-260717 A, a target substrate is rotated at a high speed (a first rotation speed) while the resist liquid is supplied onto substantially the center of the target substrate. The supplied resist liquid is applied onto the target substrate while spreading outward in a radial direction.
After the resist liquid is supplied, the rotation speed of the target substrate decreases to a low speed (a second rotation speed), so that a film thickness of the resist liquid is adjusted.
Finally, the rotation speed of the target substrate increases to a medium speed (a third rotation speed). This causes the residual resist liquid to be shaken off.
In a resist coating method and a resist coating apparatus described in JP 2007-115907 A, the rotation speed of the target substrate decreases to a rotation speed that is lower than the first rotation speed and higher than the second rotation speed, and then decreases to the second rotation speed.
In a resist coating method and a resist coating apparatus described in JP 2007-115936 A, when the rotation speed of the target substrate decreases from the first rotation speed to the second rotation speed, deceleration (speed reduction ratio) decreases as the rotation speed of the target substrate is close to the second rotation speed.
JP 11-260717 A, JP 2007-115907 A and JP 2007-115936 A describe that the foregoing methods and apparatuses allow for a uniform film thickness of the resist liquid and reduction in consumption of the resist liquid.
In recent years, however, further reduction in consumption of the resist liquid is required. In the methods and apparatuses of JP 11-260717 A, JP 2007-115907 A and JP 2007-115936 A, film thickness uniformity of the resist liquid tends to be degraded with decreasing the consumption of the resist liquid. Therefore, the consumption of the resist liquid cannot be sufficiently reduced.